Jeudi 12 dĂ©cembre 2024 à 14h00 (Salle de confĂ©rence du bâtiment 16 Ă Meudon)
Louise BREUVAL (Space Telescope Science Institute)
The 5-sigma tension between the local measurement and the early universe prediction of the Hubble constant (H0) may be the most exciting development in modern cosmology, pointing towards the possibility of new physics beyond lambda-CDM. In my talk, I will present the latest H0 measurement by the SH0ES team, based on the Cepheid and Type Ia supernova distance ladder, and will discuss recent improvements from Gaia, HST and JWST.
Lundi 9 dĂ©cembre 2024 à 16h00 (Salle de confĂ©rence du bâtiment 17)
Yaniss NYFFENEGGER
Mardi 3 dĂ©cembre 2024 à 16h00 (Salle de confĂ©rence du bâtiment 17)
Adrien MASSON (LESIA)
Some exoplanets orbit so close to their star that their atmosphere can be partially “blown away” by intense stellar radiation. This phenomenon of atmospheric escape plays a key role in planetary evolution, shaping the structure of the upper atmosphere. Photo-evaporation may even lead to the formation of super-Earth planets through the complete evaporation of mini-Neptunes’ atmospheres. In recent years, the study of the metastable helium triplet in the infrared (1083.3 nm) has made it possible to probe atmospheric escape processes from the ground using high-resolution spectrographs, enabling unprecedented measurements. We analyzed the transits of 15 exoplanets observed with SPIRou (CFHT, R=70,000), searching for helium signatures to characterize these atmospheric losses. In this seminar, I will present the physical processes at play in these extreme environments and the analytical tools and models we developed to interpret our observations.
The talk will be available via Zoom at : Zoom Link.
